Example #1
0
  static byte[] buildDH(DHPublicKey key) {
    DataByteOutputStream out = new DataByteOutputStream();
    BigInteger p = key.getParams().getP();
    BigInteger g = key.getParams().getG();
    BigInteger y = key.getY();

    int pLength, gLength, yLength;
    if (g.equals(TWO) && (p.equals(DHPRIME768) || p.equals(DHPRIME1024))) {
      pLength = 1;
      gLength = 0;
    } else {
      pLength = BigIntegerLength(p);
      gLength = BigIntegerLength(g);
    }
    yLength = BigIntegerLength(y);

    out.writeShort(pLength);
    if (pLength == 1) {
      if (p.bitLength() == 768) out.writeByte((byte) 1);
      else out.writeByte((byte) 2);
    } else out.writeBigInteger(p);
    out.writeShort(gLength);
    if (gLength > 0) out.writeBigInteger(g);
    out.writeShort(yLength);
    out.writeBigInteger(y);

    return out.toByteArray();
  }
Example #2
0
 public static void main(String args[]) throws Exception {
   Scanner cin = new Scanner(System.in);
   BigInteger s, M;
   int p, i;
   while (cin.hasNext()) {
     p = cin.nextInt();
     s = BigInteger.valueOf(4);
     M = BigInteger.ONE;
     M = M.shiftLeft(p).subtract(BigInteger.ONE);
     for (i = 0; i < p - 2; ++i) {
       s = s.multiply(s).subtract(BigInteger.valueOf(2));
       while (s.bitLength() > p) {
         s = s.shiftRight(p).add(s.and(M));
       }
     }
     if (s.compareTo(BigInteger.ZERO) == 0 || s.compareTo(M) == 0) {
       System.out.println(0);
       continue;
     }
     String ans = "";
     while (s.compareTo(BigInteger.ZERO) > 0) {
       long buf = s.mod(BigInteger.valueOf(16)).longValue();
       ans += Integer.toHexString((int) buf);
       s = s.divide(BigInteger.valueOf(16));
     }
     for (i = ans.length() - 1; i >= 0; --i) System.out.print(ans.charAt(i));
     System.out.println();
   }
 }
Example #3
0
 private void makeKeys() {
   PrimeGenerator pg = new PrimeGenerator(513, 10, sr);
   do {
     p = pg.getStrongPrime();
   } while (p.subtract(BigIntegerMath.ONE).mod(BigIntegerMath.THREE).equals(BigIntegerMath.ZERO));
   do {
     q = pg.getStrongPrime();
   } while (q.subtract(BigIntegerMath.ONE).mod(BigIntegerMath.THREE).equals(BigIntegerMath.ZERO));
   modulus = p.multiply(q);
   // Use 3 as enciphering exponent - OK since we are using salt
   decipherExp =
       BigIntegerMath.THREE.modInverse(
           p.subtract(BigIntegerMath.ONE).multiply(q.subtract(BigIntegerMath.ONE)));
   ciphertextBlockSize = (modulus.bitLength() - 1) / 8 + 1;
   // Maximum size of plaintext is 6 bytes less than ciphertext
   // 1 to get under modulus
   // 4 for the salt
   // 1 for a pad byte
   plaintextBlockSize = ciphertextBlockSize - 6;
 }